Constant current transformers



Sept. 29, 1959 c. DUENKE EIAL 2,906,976

CONSTANT CURRENT TRANSFORMERS 3 Sheets-Sheet 1 Filed Dec. 23. 1955 /NVNTOEJ CLARE/V656. DUENKE Pen-2 M MUJCHO/VG Sept. 29, 1959 c. G. DUENKE EI'AL 2,

CONSTANT CURRENT TRANSFORMERS Filed Dec. 23. 1955 3 Sheets-Sheet 2 //v VE/V TOR; c4 nee/v0: q. our/VA: PE r512 M MUJGHONG Sept; 29, 1959 Filed Dec. 23. 1955 C. G- DUENKE ET AL CONSTANT CURRENT TRANSFORMERS 3 Sheets-Sheet 3 7 $10.. YTT

//v1 1v r0125 CLARENCE DUENKE PE r52 M MUJCHONG United States, Patent CONSTANT CURRENT TRANSFORMERS Clarence G. Duenke, Webster Groves, and Peter W.

Muschong, St. Louis, Mo., assignors to Mol'oney Electric Company, St. Louis, Mo., a corporation of Delaware Application December 23, 1955, Serial No. 555,035

2 Claims. (Cl. 336-40) This invention relates generally to constant current transformers which are designed to maintain normal rated lamp current on series street or highway lighting circuits under varying conditions of loading, primary voltage and frequency. Tests show that lamp life is greatly reduced with but a small increase in current above rated values, and tests also show that light output decreases rapidly as the current is reduced below normal rating. It is, therefore, essential that the transformer provides very close regulation of secondary current and responds quickly to changes in load, primary voltage and frequency in order to provide maximum lamp life at full rated light output. To obtain constant current under varying load conditions it is necessary, in the use of constant current transformers of the moving coil type to which this invention relates, that the sum of the internal impedance of the transformer and the impedance of the series lighting circuit remain substantially constant at all times. When the impedance of the lighting circuit decreases due to burned-out lamps, it is necessary 'that the impedance of the transformer be correspondingly increased in order to maintain normal lamp current. The transformer, therefore, must be a variable impedance mechanism. Variable impedance is obtained in the case of constant current transformers of the moving coil type, through the use of the force of repulsion created when current flows in the two windings of the transformer, and through the change in reactance resulting through the change in magnetic leakage when the distance between the windings is varied. Reactance is minimum when the windings are together and maximum when the windings are farthest apart.

Prior to this invention, when the constant current transformer was energized with the secondary connected to a series lighting circuit load, the flow of current in the two coils resulted in a force of repulsion that tended to push the coils apart, and in order to obtain the desired secondary current Weights were added to the free end of the upper coil support to oppose the force of repulsion, until the distance between the coils had been reduced to the extent that the transformer impedance, together with the load impedance, resulted in normal lamp current. Change in load caused the force of repulsion to increase or decrease, the positions of the coils then changing to compensate for the change in load impedance, and normal rated current is again attained.

The predominant object of this invention is to provide a constant current transformer of the moving coil type with improved means, in addition to the weights for offsetting the force of repulsion of the coils, this improved means being operable from the exterior of the casing of the transformer by a suitable handle and including spring means which serves to aid the weights in opposing the force of repulsion of the coils, thus avoiding the need formerly necessary to attain the proper weight required of the weights through the use of shims, or other means.

Fig. l is an elevational view of a constant current ICC transformer of the moving coil type made in accordance with this invention, the casing of the transformer being shown partly in section and partly by broken lines.

Fig. 2 is an end elevational view of the mechanism of the transformer shown in Fig. 1, the casing of the transformer being omitted in Fig. 2.

Fig. 3 is a top plan view of the constant current transformer shown in Fig. 1.

Fig. 4 is a fragmentary elevational detail of the improved means for aiding the weights in opposing the force of repulsion of the coils.

Fig. 5 is a fragmentary section taken on line 55 of Fig. 4.

In the drawings, wherein is shown for purposes of illustration, merely, one embodiment of the invention, A designates the improved constant current transformer generally. The constant current transformer A includes an outer casing 1 which encloses the mechanism of the transformer, said mechanism being submerged in oil within the outer tank 1. The mechanism of the transformer that is enclosed within the outer casing 1 comprises a frame structure 2 that includes a pair of lower base members 3, a plurality of vertical members 4 which preferably are formed of wood, and a pair of top members 5, said plurality of vertical members being suitably secured, at their lower ends, to and being supported by said base members 3, and said top members 5 being suitably secured to said vertical members at their upper ends. The base member 3 has attached thereto foot members 6 upon which the frame structure rests, as shown to good advantage in Fig. 1.

The mechanism which is enclosed within the casing 1 includes an upper coil 7 and a lower coil 8, the upper coil 7 being mounted on a supporting member 9, While the coil 8 is mounted on a supporting member 10. The supporting member 9 on which the upper coil 7 is mounted is hingedly supported at one end thereof by a shaft 11 that extends transversely of the frame 2, and the supporting member 10 on which the lower coil 8 is mounted is supported at one end thereof by a shaft 12 which likewise extends transversely of the frame 2, the supporting members 9 and 10 being hingedly supported by their respective shafts at opposite ends thereof and being adapted to swing from their pivots toward and from each other. At each side of the constant current transformer is a pair of pulleys 13 and 14, each pair of pulleys being mounted on a shaft 15 which is supported by the top members 5 of the frame structure 2, and said shaft being extended transversely of said frame structure. Mounted on each pair of pulleys 13 and 14 is a metallic band 16, said bands each moving on and with the pair of pulleys with which it is related, and

each band being secured at one end thereof to a member 17 that is fixed to the free end portion of supporting member which supports the coil 8, and each band is secured at its opposite end to a member 18 that is fixed to the free end portion of a supporting member which supports the coil 7. The members 17 and 18 are each secured to the free end portions of the supporting members 9 and 10 by means of a bolt 19 and the end portions of the metallic bands are secured to said members by the same bolts, as shown to good advantage in Fig. 1, the two members 17 and the two members 18 of the supporting members 9 and 10 being tied together by tie rods 20. Mounted on the supporting member 9 of the upper coil 7 at the free end thereof is a pair of weight structures 21 for counter-balancing the forces of repulsion between primary and secondary windings, said weight structures being secured in place by rod and nut assemblies 22.

The improved constant current transformer of this invention includes auxiliary biasing means 23, addition to the weight structures 21, for ofisetting the force of repulsion of the coils, said means comprising a coil spring 24 which is secured through the instrumentality of a clip 25 to one of the hinge members 26 which are fixed to the hinged end portion of the supporting member 9 on which the upper coil 7 is mounted. The hinge members 26 have portions 27 which embrace the shaft 11 and thereby provide for swinging movement of the supporting member 9 and the coil 7 relative to said shaft 11. The end of the coil spring'24, opposite to the end thereof which is attached to a hinge member 26, is connected to a turnbuckle 28 and this turnbuckle at its opposite end is fixedly attached to the outer end of an arm 29, said arm being mounted on a shaft 30 at one end thereof, and said shaft 30 extending through a bearing member 31 which is secured to the wall of the casing 1 and is provided with a flange 3-2 at its outer end. The flange 32 of the bearing member 31 is provided with spaced openings 33 formed therein on an arc of a circle, and a handle 34 which is mounted on and is secured to the outer end portion of the shaft 30 is provided with a boss 35, located intermediate of its ends which receives the outer end portion of the shaft 30. The handle 34 is also provided with an enlarged, tubular portion 36 and its outer end through which a plunger 37 extends, said plunger having a flanged portion 37 of slightly enlarged diameter at its outer end, and a part of said plunger being embraced by a coil spring 38 which serves to urge said plunger in an inward direction.

In the operation of the constant current transformer of this invention the weight structures 21 are arranged in place in the transformer and these weight structures need not have a weight which is precisely the proper weight required to oppose the force'of repulsion between the coils. The weight of the weight structures is of only the approximate proper weight required to oppose the force of repulsion, and the precise weight may be attained by moving the handle 34 of the means 23 either to the right or left of a center line drawn vertically thr'ough the shaft 30 and the plunger 37. Movement of the handle is obtained by first drawing the plunger 37 outwardly against the force of the coil spring 38 to'free the inner end of said plunger from the opening 33 in which it is disposed, whereupon the handle 34 may be rotated as desired, and the plunger is permitted to enter a desired new opening 33 to lock the weight structures at the precise required weight. It will be noted that the clip 25 which connects the coil spring 24 to a hinge member 26 is connected to the portion 27 of said hinge member and hence the force exerted by the coil spring 24 on the supporting member 9 that supports the upper coil 7 will tend to rotate said supporting member 9.

4 When the handle 34 is shifted to the right or left as previously explained, the tension of the coil spring -24 is increased or decreased as desired.

We claim:

1. In a constant current trans-former comprising a casing, upper and lower coil supports in the casing, the upper support being mountedfor pivotal movement on a horizontal axis adjacent one side of the casing and extending toward the opposite side of the casing, the lower support being mounted for pivotal movement on a horizontal axislparallelito the axis of the upper support adjacent the opposite side of the casing and extending toward said one side of the casing, a coil on the upper support between its pivotal axis and said opposite side of the casing, a coil on the lower support between its pivotal axis and said one side of the casing, and means connecting the end of the upper support toward said opposite side of the casing and the end of the lower support toward said one side of the casing for equidistant movement thereof in opposite directions: a weight adjacent said end of the upper supportacting to bias the supports and coils for movement toward one another with a force approximating a predetermined force of repulsion, and auxiliary biasing means capable of fine adjustment for bringing the total bias on the supports and coils intotprecise correspondence with said predetermined force of repulsion, said auxiliary biasing means comprising a tension spring having one end connected to the upper coil support at a point between the pivotal axis thereof and said one side of the casing and closely adjacent said pivotal axis, said spring extending upward in the casing from the upper coil support adjacent said one side of the cassing, means for adjusting the tension of the spring comprising a shaft journalled in said one side of the casing above the upper coil support, the upper end of the spring being connected to said shaft within the casing at a point spaced from the pivotal axis of the shaft, said shaft'being rotatable from outside the casing to different positions for adjusting the tension of the spring, and means for holding said shaft in different rotary positions of adjustment.

2. In a constant current transformer as set forth in claim 1, said holding means comprising a handle on the shaft outside the casing, an element mounted on the UNITED STATES PATENTS 1,435,195 Atherton Nov. 14, 1922 1,469,213 Douglass .."Oct. 2, 1923 2,337,346 Peterson Dec. 21, 1943 

